There are many, and I believe it is harder to spot the underrated ones to the overrated.
William Fichtner - one hell of a character actor, should get some lead roles before he gets too old.
Paul Walker - He really is a good actor, when he chooses the right movies. For example, he was great in the fast and the furious, and in eight below.
Kevin Bacon - the guy has been in many many movies and acted gracefully in many of them, yet has not even received a single oscar nomination.